Embodiments of the invention relate to a printing blanket for use in lithographic printing including a compressible layer and a reinforcing layer, and more particularly, to a printing blanket including a polymeric fabric reinforcing layer or a polymeric reinforcing layer which provides a smooth surface to support an outer print surface layer to provide improved print performance while enabling a reduction in the overall thickness of the reinforcing layer.
One of the most common commercial printing processes is offset lithography. In this printing process, ink is offset from a printing plate to a rubber-surfaced printing blanket or sleeve before being transferred to a substrate, such as paper. Where a printing blanket is used, it is typically constructed using a fabric or reinforced polymer base, and then the layers comprising the blanket are attached to the base. Such layers can include one or more compressible layers, one or more reinforcing layers, and an outer print surface layer.
The reinforcing layer for current commercial blankets typically comprises a fabric layer, which is comprised of natural or synthetic materials such as polyester, cotton, or blends thereof. The fabric layer stabilizes and reinforces the other functional layers on the blanket. However, a disadvantage of such materials is that the resulting reinforcing layer does not exhibit surface uniformity, which can result in the problem of threads or textures from the underlying reinforcement layer causing non-uniformities in the printing face, and ultimately the printed image. The fabric may also allow liquid printing chemicals such as inks, fountain solution, and blanket wash to wick into the fabric, potentially causing printing problems and reducing blanket life.
In addition, the reinforcing layer is typically about 0.008 to 0.010 inches (0.2 mm to 0.254 mm) in thickness. In order to improve print quality, it would be desirable to provide a printing blanket in which the reinforcing layer has a reduced thickness, which does not cause non-uniformities in the printing face, and which restricts the penetration of printing chemicals. Such a thinner reinforcing layer would allow the use of a thicker compressible layer without increasing the overall thickness of the blanket. This, in turn, would avoid undesirable compression set and improve print quality. Accordingly, there is a need in the art for a printing blanket which provides improved print performance.